microbial genetics

1. Microbiology
B.E Pruitt & Jane J. Stein
AN INTRODUCTION
EIGHTH EDITION
TORTORA • FUNKE • CASE
Chapter 8, part A
Microbial Genetics

2. Terminology
• Genetics Study of what genes are, how they
carry information, how information is
expressed, and how genes are
replicated
• Gene Segment of DNA that encodes a
functional product, usually a protein

3. Terminology
• Genome All of the genetic
material in a cell
• Genomics Molecular study of
genomes
• Genotype Genes of an
organism
• Phenotype Expression of the genes

4. E. coli
Figure 8.1a

5. Flow of Genetic Information
Figure 8.2

6. • Polymer of nucleotides:
adenine, thymine,
cytosine, guanine
• Double helix associated
with proteins
• "Backbone" is
deoxyribose-phosphate
• Strands held together by
hydrogen bonds
between AT and CG
• Strands are antiparallel
DNA
Figure 8.4

7. DNA
Figure 8.3

8. DNA
Figure 8.5

9. • DNA is copied by DNA polymerase
– In the 5′ → 3′ direction
– Initiated by an RNA primer
– Leading strand synthesized continuously
– Lagging strand synthesized discontinuously
– Okazaki fragments
– RNA primers are removed and Okazaki
fragments joined by a DNA polymerase and
DNA ligase
– See web sites
• http://bioteach.ubc.ca/TeachingResources/MolecularBiology/DNAReplication.swf
• http://www.ncc.gmu.edu/dna/repanim.htm
• http://www.mun.ca/biology/scarr/3250_DNA_replication_&_transcription.htm
•
http://www.nobel.se/medicine/educational/dna/a/replication/replication_ani.html
• http://www.nobel.se/medicine/educational/dna/a/replication/lagging_ani.html
DNA

10. DNA
Figure 8.6

11. • DNA replication is semiconservative
DNA
Figure 8.7

12. • DNA is transcribed to make RNA (mRNA,
tRNA, and rRNA)
• Transcription begins when RNA polymerase
binds to the promotor sequence
• Transcription proceeds in the 5′ → 3′
direction
• Transcription stops when it reaches the
terminator sequence
• Web sites:
– http://www.nobel.se/medicine/educational/dna/b/transcription/
Transcription

13. Figure 8.8

14. RNA processing in Eukaryotes
Figure 8.12

15. • mRNA is
translated in
codons (3
nucleotides)
• Translation of
mRNA begins at
the start codon:
AUG
• Translation
ends at a STOP
codon: UAA,
Translation
Figure 8.2

16. Translation
Figure 8.9